Process for production of benzonitrile and benzyl alcohol

ABSTRACT

A process for producing a fluorinated benzonitrile comprising hydrogenolyzing a fluorinated dicyanobenzene substituted with 1 to 4 fluorine atoms and having the remainder which may be substituted with a chlorine atom in the presence of a catalyst to cause hydrodecyanation of only the cyano group of one side and a process for producing a fluorinated benzyl alcohol comprising reducing the fluorinated benzonitrile and hydrolyzing the fluorinated benzonitrile and reducing the resultant corresponding fluorinated benzoic acid to convert the cyano group to a hydroxymethyl group.

TECHNICAL FIELD

The present invention relates to a process for producing fluorinatedbenzonitrile and fluorinated benzyl alcohol useful as intermediates forthe production of cyclopropane carboxylic acid esters having superiorinsecticidal action, and other agrochemicals, drugs, etc.

BACKGROUND ART

It has been disclosed that a cyclopropane carboxylic acid ester of afluorinated benzyl alcohol having the general formula: ##STR1## whereina and b independently represent 1, 2, 3, or 4 and c represents 0, 1, or2 has a high insecticidal activity (DE-A-2658074 etc.). In particular,it has been disclosed that a cyclopropane carboxylic acid ester of2,3,5,6-tetrafluorobenzyl alcohol has a high insecticidal activity andthat it has a lower toxicity to mammals compared with a cyclopropanecarboxylic acid ester of pentafluorobenzyl alcohol, and therefore, is asuperior insecticide (DE-A-3705224).

As a process for producing the fluorinated benzyl alcohol having thegeneral formula (I), a process has been proposed of reducing a halogensubstituted benzoic acid derivative with a metal hydrides such as NaBH₄,LiAlH₄. For example, DE-A-3714602 discloses a process for producing2,3,5,6-tetrafluorobenzyl alcohol by reacting 2,3,5,6-tetrafluorobenzoicacid with NaBH₄ followed by treating with an alkylation agent. Further,DE-A-2658074, 2714042, and 2661074 disclose processes for producing forreducing polyfluorobenzoyl fluoride with NaBH₄ to producepolyfluorobenzyl alcohol and processes for reducing polyfluorobenzoylfluoride with LiAlH₄ to produce a polyfluorobenzyl alcohol wherein oneor more fluorine substituted groups are defluorinated. EP-A-31199discloses a process for reacting 1,2,4,5-tetrafluorobenzene and n-butyllithium and then reacting with carbon dioxide to form2,3,5,6-tetrafluorobenzoic acid, which is reduced with LiAlH₄ to produce2,3,5,6-tetrafluorobenzyl alcohol.

On the other hand, electrolytic reduction processes have also beenproposed as processes for the production of a fluorinated benzyl alcoholhaving the general formula (I). For example, JP-A-1-119686 discloses aprocess for the production of 2,3,5,6-tetrafluorobenzaldehyde and2,3,5,6-tetrafluorobenzyl alcohol by electrolytic reduction ofpentafluorobenzoic acid using a solid metal or a solid alloy as acathode and an aqueous solution of sulfuric acid, hydrochloric acid,phosphoric acid, or sulfonic acid as an electrolyte. Further,JP-A-63-206491 discloses production of 2,3,5,6-tetrafluorobenzyl alcoholas a mixture with pentafluorobenzyl alcohol so as to electrolyticallyreduce pentafluorobenzoic acid using a solid metal or solid alloy as acathode and an aqueous sulfuric acid solution as an electrolyte. Thereare many reports on processes for production of a fluorinated benzylalcohol by electrolytic reduction, but in the same way as above, abenzyl alcohol is produced as a mixture in each case ("J. Electroanal.Chem.", 1991, p. 215; "J. Electroanal. Chem.", 1987, p. 315; "J. Chem.Soc. Perkin Trans I", 1972, p. 189; "J. Appl. Electrochem.", 1992, p.1082; "Denkikagaku oyobi Kogyobutsurikagaku", 1990, p. 83; etc.)

DISCLOSURE OF INVENTION

The object of the present invention is to produce a fluorinated benzylalcohol having the general formula (I) and the intermediates thereof,the fluorinated benzonitrile having the general formula (III), by anindustrially advantageous process at a high yield, more particularly, toproduce 2,3,5,6-tetrafluorobenzonitrile and 2,3,5,6-tetrafluorobenzylalcohol at a high purity and a high yield, which are useful asproduction intermediates of pyrethroids having a high insecticidalactivity and a low toxicity to the human body.

In accordance with the present invention, there is provided a processfor producing a fluorinated benzonitrile comprising the step of:

hydrogenolyzing a fluorinated dicyanobenzene substituted with 1 to 4fluorine atoms and having the remainder which may be substituted with achlorine atom in the presence of a catalyst so as to causehydrodecyanation of only the cyano group of one side.

In accordance with the present invention, there is also provided aprocess for producing a fluorinated benzyl alcohol having the formula(I): ##STR2## wherein a and b independently represent 1, 2, 3, or 4 andc represents 0, 1, or 2 comprising the steps of:

using a fluorinated dicyanobenzene having the formula (II) ##STR3##wherein a, b, and c are as defined above, as a starting material, andcausing hydrodecyanation of only the cyano group of one side so as toproduce a fluorinated benzonitrile having the formula (III): ##STR4##wherein a, b, and c are as defined above and then converting the cyanogroup of the fluorinated benzonitrile to a hydroxymethyl group to formthe fluorinated benzonitrile to a hydroxymethyl group.

In accordance with the present invention, there is further provided aprocess for producing a fluorinated benzyl alcohol comprising reducingthe above fluorinated benzonitrile, or hydrolyzing the fluorinatedbenzonitrile followed by reducing the resultant correspondingfluorinated benzoic acid, to convert the cyano group to a hydroxymethylgroup.

Note that the fluorinated benzonitrile having the general formula (III)may specifically be reduced to a; a fluorinated benzaldehyde having theformula (IV): ##STR5## wherein a, b, and c are as defined above,followed by reducing the aldehyde group of the fluorinated benzaldehydeto a hydroxymethyl group to form the fluorinated benzyl alcohol havingthe general formula (I).

Further, it is possible to reduce the cyano group of the fluorinatedbenzonitrile having the above formula (III) to a hydroxymethyl group bya single stage reaction without isolating the fluorinated benzaldehydeto obtain the fluorinated benzyl alcohol having the general formula (I).

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be explained in further detail. Accordingto the present invention, it is possible to hydrogenolyze thefluorinated dicyanobenzene having the general formula (II) through thereaction formula (V) in the presence of a catalyst to hydrodecyanateonly the cyano group of one side to produce a fluorinated benzonitrilehaving the general formula (III) and then carry out either one of thereactions shown in the reaction formulae (VI), (VII), and (VIII) toproduce a fluorinated benzyl alcohol having the general formula (I):##STR6##

Thus, according to the process of the present invention, it is possibleto produce the fluorinated benzyl alcohol having the general formula (I)by an industrially advantageous method at a high yield. It isparticularly advantageous for the production of2,3,5,6-tetrafluorobenzyl alcohol. That is, in the conventionalelectrolytic reduction process etc. of pentafluorobenzoic acid,inclusion or contamination of pentafluorobenzyl alcohol, which is thestarting material of pyrethroids having a high toxicity to mammals, intothe product is unavoidable. On the other hand, the process of thepresent invention uses tetrafluoroterephthalonitrile as a startingmaterial and hydrodecyanates only one cyano group to produce2,3,5,6-tetrafluorobenzonitrile, then converts the cyano group of the2,3,5,6-tetrafluorobenzonitrile to a hydroxymethyl group to produce2,3,5,6-tetrafluorobenzyl alcohol, and therefore, it is possible tocompletely avoid production of pentafluorobenzyl alcohol.

For the starting material of the present invention, it is possible touse the fluorinated dicyanobenzene having the general formula (II).Specifically, 2,3,5,6-tetrafluoroterephthalonitrile,3,4,5,6-tetrafluorophthalonitrile, 2,4,5,6-tetrafluoroisophthalonitrile,2,3,5-trifluoroterephthalonitrile, 2,6-difluoroterephthalonitrile,2,6-difluoro-3,5-dichloroterephthalonitrile,2,3-difluoro-5-chloroterephthalonitrile,2-fluoro-3,5-dichloroterephthalonitrile, etc. may be used. Inparticular, a 2,3,5,6-tetrafluoroterephthalonitrile of general formula(II) having a=1, b=4, and c=0 is preferably used. These fluorinateddicyanobenzenes may be produced by known methods. For example, it ispossible to produce the fluorinated dicyanobenzenes by replacing thechlorine atoms of chlorinated dicyanobenzenes obtained by chlorinationof dicyanobenzenes with fluorine by a fluorinated alkali. Morespecifically, JP-B-44-28493 discloses a process for producing2,3,5,6-tetrafluoroterephthalonitrile by reacting2,3,5,6-tetrachloroterephthalonitrile with potassium fluoride.

D. J. Milner reports the reaction of tetrafluoroterephthalonitrile withmethyl magnesium bromide to synthesize4-methyl-2,3,5,6-tetrafluorobenzonitrile (J. Organometallic Chem., 302(1986) 147). In this case, 2,3,5,6-tetrafluorobenzonitrile is obtainedas a byproduct, but the yield thereof is extremely low. Further, thisreaction requires equal moles of a Grignard reagent such as methylmagnesium bromide and the handling is also difficult, and therefore,this cannot be said to be an industrially advantageous process as aprocess for producing 2,3,5,6-tetrafluorobenzonitrile.

The hydrodecyanation reaction according to the present invention iscarried out in the presence of a catalyst by the hydrogenolysis shown inthe reaction formula (V). ##STR7##

In the present invention, as the decyanation catalyst, at least onemetal catalyst selected from metals of the Group VIII, Group IX, andGroup X of the Periodic Table such as palladium, platinum, nickel,ruthenium, rhodium may be used. In particular, palladium, platinum, andnickel may be suitably used. The catalyst may be used as it is as ametal or in the form of a supported catalyst. As the carrier of thesupported catalyst, activated carbon, silica, alumina, and the like maybe used. As specific examples of the preferable catalyst,palladium/activated carbon, palladium/silica, etc. may be mentioned.

In the present invention, the pretreating method of the catalyst inadvance in a hydrogen atmosphere is an effective means for theactivation of the catalyst. The pretreating method is not particularlylimited, but the method of holding the catalyst at a temperature fromroom temperature to about 400° C. in a hydrogen flow or in a hydrogenatmosphere is mentioned.

Further, the addition of a co-catalyst (or a catalyst promoter) iseffective for the reaction of the present invention and improves thereaction rate and the selectivity. As such a co-catalyst, aminecompounds such as ethylamine, triethylamine, chelate compounds such asethylenediaminetetraacetic acid, nitrilotriacetic acid,1,2-diaminopropanetetraacetic acid, 1,3-diamino-2-propanoltetraaceticacid, bis(2-aminoethyl)ethyleneglycoltetraacetic acid, and their alkalisalts; carboxylic acid compounds such as acetic acid, formic acid; metalsalts such as lead acetate may be used. In particular, the addition ofchelate compounds such as ethylenediaminetetraacetic acid,nitrilotriacetic acid, and alkali salts thereof improve the reactionrate and the selectivity, and therefore, these are preferably used asco-catalysts.

As the reaction solvents in the reaction of the present invention, it ispossible to use a relatively broad range of solvents. For example,aromatic hydrocarbons such as benzene, toluene, ethylbenzene, cumene,tert-butylbenzene, xylene, mesitylene; aliphatic hydrocarbons such ashexane, cyclohexanes; alcohols such as methanol, 2-propanol; ethers suchas tetrahydrofuran, 1,4-dioxane, diethylene glycol dimethyl ether;carboxylic acids such as acetic acid, formic acid; nitriles such asacetonitrile, etc. may be used. In particular, monoalkyl substitutedbenzenes such as toluene, ethylbenzene, cumene, tert-butylbenzene arepreferably used. Further, when using a reaction of a fixed bed gas phaseprocess, the reaction can be carried out in the absence of a solvent.

The type of the reaction is not particularly limited, but the liquidphase suspension bed process, fixed bed gas phase process, liquid phasefixed bed process, or batch process may be used.

The reaction temperature is not particularly limited, but it ispreferably to use a temperature from room temperature to about 400° C.In particular, when using a reaction of the fixed bed gas phase process,it is preferable to react at a temperature of 200° C. or more. Further,the reaction pressure may be in the range of atmospheric pressure to ahigher pressure. The hydrogen partial pressure is preferably in therange of 1 MPa or less.

The hydrogen in the hydrodecyanation reaction may be supplied as it isor in the form of a mixture with nitrogen gas. Note that the supply ofhydrogen gas is not essential. For example, it is also possible not tosupply hydrogen gas, but an aromatic compound having hydrogen at theα-position can be used as a hydrogen source. For example, if thereaction is carried out in the presence of a monoalkyl substitutedbenzene such as toluene, ethylbenzene, cumene in an inert gasatmosphere, it is possible to simultaneously produce benzyl cyanidesuseful as materials for synthesis of drugs together the fluorinatedbenzonitrile by the transcyanation reaction shown by the reactionformula (IX): ##STR8## wherein a, b, and c are as defined above and Rand R' are independently a hydrogen atom or an alkyl group.

The fluorinated benzonitrile having the general formula (III) obtainedby the above reaction may be purified by separating the catalyst byfiltration, centrifugation, decantation, and other operations, followedby distillation etc. Further, it is also possible to use the reactionmixture for the next step as it is, without purification. For example,it is possible to supply the reaction mother solution, from which thecatalyst is separated, to the next step and carry out the reaction forconverting the cyano group to a hydroxymethyl group.

The fluorinated benzonitrile having the general formula (III) isconverted to the fluorinated benzyl alcohol having the general formula(I) by any reaction of the reaction formulae (VI), (VII), and (VIII):##STR9##

According to the reaction formula (VI), it is possible to reduce thefluorinated benzonitrile having the general formula (III) to thefluorinated benzaldehyde having the general formula (IV), then reducethe aldehyde group to a hydroxymethyl group to produce the fluorinatedbenzyl alcohol having the general formula (I).

The preparation for the fluorinated benzaldehyde is carried out byhydrogen reduction in the presence of a catalyst. This reaction proceedsaccording to the mechanism of the reaction formulae (X) and (XI). Thatis, hydrogen is added to the cyano group and the corresponding imine isproduced. The reaction intermediate imine is hydrolyzed to synthesizethe aldehyde. ##STR10##

This reaction is carried out in the presence of a catalyst. As thecatalyst, any one of metal catalysts selected from the Group VIII, GroupIX, and Group X of the Periodic Table such as nickel, palladium,platinum may be used. In particular, it is possible to preferably use anickel or palladium catalyst. These catalysts may be used as they are asmetals or in the form of a supported catalyst. As the support, activatedcarbon, silica, alumina, and the like may be used. As specific examplesof preferable catalysts, Raney nickel, palladium/activated carbon, etc.may be exemplified.

The addition of a co-catalyst is effective for this reaction. Salts oroxides of lead, cadmium, antimony, bismuth, zinc, iron, and copper maybe used as the co-catalyst. In particular, copper compounds such ascopper acetate and lead compounds such as lead acetate, are effectivefor suppressing the production of by-products such as amines. Further,the addition of an acid is effective for this reaction. It is believedthat the acid promotes the hydrolysis reaction of (XI), and therefore,suppresses the production of the byproduct amines resulting from theexcessive reduction of the imines produced by the reaction of (X). Asthe acid, formic acid, acetic acid, monochloroacetic acid,dichloroacetic acid, trifluoroacetic acid, sulfuric acid, hydrochloricacid, phosphoric acid, and the like may be used. In particular,chloroacetic acids, fluoroacetic acids, formic acid, and acetic acid maybe preferably used.

As the solvent of the reaction, alcohols such as methanol, ethanol,2-propanol, ethers such as 1,4-dioxane, tetrahydrofuran, and carboxylicacids such as acetic acid, formic acid may be used. In particular,methanol and acetic acid are preferably used. Further, the amount of thewater added is preferably in the range of 1 to 1000 times molar amountrelative to the raw material.

The form of the reaction is not particularly limited, but the liquidphase suspension bed process, fixed bed gas phase process, liquid phasefixed bed process, or batch process may be used.

The reaction temperature is not particularly limited, but it ispreferably to use a temperature from ordinary temperature to about 200°C. The reaction pressure may be in the range of atmospheric pressure toa higher pressure. The hydrogen partial pressure is preferably in therange of 0.1 MPa or less.

The fluorinated benzaldehyde having the general formula (IV) obtained bythe above reaction may be purified by separating the catalyst byfiltration, centrifugation, decantation, and other operations, thendistillation etc. Further, it is also possible to use the reactionproduct for the next step as it is, without purification. For example,it is possible to supply the reaction mother solution, from which thecatalyst is separated, to the next step and carry out the reaction forconverting the aldehyde group to the corresponding hydroxymethyl group.

The benzaldehyde having the general formula (IV) produced by the abovereaction is converted to the benzyl alcohol having the general formula(I) shown by the reduction reaction of the reaction formula (XII).##STR11##

The reaction proceeds in the presence of a metal catalyst such asnickel, palladium, platinum, ruthenium, cobalt, copper. In particular,it is possible to preferably use a nickel, palladium, or platinumcatalyst. These catalysts may be used as they are as metals or in theform of supported catalysts. As the support, activated carbon, silica,alumina, and the like may be used. As specific examples of preferablecatalysts, Raney nickel, palladium/activated carbon, etc. may bementioned. Further, metal hydrides such as NaBH₄, LiAlH₄, may be used toreduce the aldehyde to the alcohol.

As the reaction solvent, alcohols such as methanol, ethanol, 2-propanol,ethers such as 1,4-dioxane, tetrahydrofuran, carboxylic acids such asacetic acid, formic acid may be used. In particular, methanol ispreferably used.

The form of the reaction is not particularly limited, but the liquidphase suspension bed process, fixed bed gas phase process, liquid phasefixed bed process, or batch process may be used.

The reaction temperature is not particularly limited, but it ispreferably to use a temperature from ordinary temperature to about 100°C. The reaction pressure may be in the range of atmospheric pressure toa higher pressure. The hydrogen partial pressure is preferably in therange of 1 MPa or less.

The benzyl alcohol having the general formula (I) obtained by the abovereaction may be purified by separating the catalyst by filtration,centrifugation, decantation, and other operations, then distillationetc.

Next, the method of direct reduction of the cyano group of thebenzonitrile having the general formula (III) to a hydroxymethyl groupby the reaction of the reaction formula (VII) to produce the benzylalcohol having the general formula (I) will now be explained.

This reaction is shown by the reaction formula (XIII). The mechanism ofthis reaction resides in the successive proceedings of each elementreaction, i.e., the production of imines by the reduction of the cyanogroup in the reaction formula (X), the production of aldehydes byhydrolysis of imine of the reaction formula (XI), and the production ofalcohol by the reduction of the aldehyde of the reaction formula (XII).##STR12##

The production process of the benzyl alcohol having the general formula(I) according to this reaction is the most superior process in the pointthat the process is tremendously simplified.

The reaction proceeds in the presence of a catalyst. As the catalyst, atleast one metal catalyst selected from the group consisting of metals ofthe Group VIII, Group IX, and Group X of the Periodic Table such asnickel, palladium, platinum, may be used. In particular, it is possibleto preferably use a nickel catalyst. These catalysts may be used as theyare as metals or in the form of supported catalysts. As the support,activated carbon, silica, alumina, and the like may be used. As specificexamples of preferable catalysts, Raney nickel may be mentioned.

Addition of a co-catalyst is effective for this reaction. Salts oroxides of lead, cadmium, antimony, bismuth, zinc, iron, and copper maybe used as the co-catalyst. In particular, copper compounds such ascopper acetate and lead compounds such as lead acetate are effective forsuppressing the production of by-products such as amines. Further, theaddition of an acid is effective for this reaction. As the acid, formicacid, acetic acid, monochloroacetic acid, dichloroacetic acid,trifluoroacetic acid, sulfuric acid, hydrochloric acid, phosphoric acid,and the like may be used, but especially, chloroacetic acids,fluoroacetic acids, formic acid, and acetic acid may be preferably used.

As the solvent of the reaction, alcohols such as methanol, ethanol,2-propanol, ethers such as 1,4-dioxane, tetrahydrofuran, carboxylicacids such as acetic acid, formic acid, may be used. In particular,methanol is preferably used. Further, the amount of the water added ispreferably in the range of 1 to 1000 times molar amount relative to theraw material.

The form of the reaction is not particularly limited, but the liquidphase suspension bed process, fixed bed gas phase process, liquid phasefixed bed process, or batch process may be used.

The reaction temperature is not particularly limited, but it ispreferably to use a temperature from ordinary temperature to about 200°C. The reaction pressure may be in the range of atmospheric pressure toa higher pressure. The hydrogen partial pressure is preferably in therange of 1 MPa or less.

The benzyl alcohol having the general formula (I) obtained by thereaction may be purified by separating the catalyst by filtration,centrifugation, decantaiton, and other operations, then distillationetc.

Further, it is possible to hydrolyze the cyano group of the benzonitrilehaving the general formula (III) to a carboxyl group by the reactionhaving the reaction formula (VIII) and then reduce the carboxyl group toa hydroxymethyl group to produce the benzyl alcohol having the generalformula (I).

The reaction for hydrolyzing the cyano group to convert it to a carboxylgroup proceeds in the presence of an acid or alkali according to knownreactions. In the present invention, it is also possible to use an acidor alkali to hydrolyze the general formula (III) to form benzoic acid,but an acid is preferably used to prevent the simultaneous occurrence ofhydrolysis of the fluoro substituted group. As the preferably usedacids, sulfuric acid, hydrochloric acid, nitric acid, and the like maybe mentioned.

By reducing the carboxyl group of the obtained benzoic acids tohydroxymethyl groups, the benzyl alcohol having the general formula (I)is produced. This reduction reaction is a known reaction. For example,it is performed using metal hydrides such as NaBH₄, LiAlH₄. Morespecifically, DE-A-3714602 discloses a process of reacting2,3,5,6-tetrafluorobenzoic acid with NaBH₄ to produce 2,3,5,6-benzylalcohol.

EXAMPLES

The present invention will now be explained in detail by Examples, butthe scope of the present invention is of course not limited to theseExamples.

Example 1

(Hydrodecyanation Reaction)

100 g of toluene, 0.20 g of 5% palladium/activated carbon, and 1.0 g of2,3,5,6-tetrafluoroterephthalonitrile were added to a 500 cc glassthree-necked flask with a reflux condenser in a nitrogen atmosphere. Thegas phase was sufficiently substituted by hydrogen gas, then a hydrogenballoon was attached to the top portion of the reflux condenser and theresulting mixture was heated to 100° C. After 8 hours reaction, thereaction solution was analyzed by gas chromatography, whereupon the rateof conversion of 2,3,5,6-tetrafluorotetraphthalonitrile was found to be98%, the yield of 2,3,5,6-tetrafluorobenzonitrile (based on2,3,5,6-tetrafluoroterephthalonitrile) was 73%.

Example 2

(Hydrodecyanation Reaction)

Using a method similar to Example 1 and using 75 g of formic acid, 5.0 gof Raney nickel, and 2.5 g of 2,3,5,6-tetrafluoroterephthalonitrile, areaction was carried out at 80° C. for 30 minutes. The conversion of2,3,5,6-tetrafluoroterephthalonitrile was found to be 82% and the yieldof 2,3,5,6-tetrafluorobenzonitrile (based on2,3,5,6-tetrafluoroterephthalonitrile) was 35%.

Example 3

(Hydrodecyanation Reaction)

A reaction was carried out in the same way as in Example 1, except that1.0 g of triethylamine was added as a co-catalyst and the reaction timewas made 7 hours. The conversion of2,3,5,6-tetrafluoroterephthalonitrile was found to be 100% and the yieldof 2,3,5,6-tetrafluorobenzonitrile was 77%.

Example 4

(Hydrodecyanation Reaction)

By a method similar to Example 1 and using 125 g of diethyleneglycoldimethyl ether and 1.60 g of 5% palladium/activated carbon, a reactionwas carried out at 100° C. for 1.5 hours. The conversion of2,3,5,6-tetrafluoroterephthalonitrile was found to be 100% and the yieldof 2,3,5,6-tetrafluorobenzonitrile (based on2,3,5,6-tetrafluoroterephthalonitrile) was 37%.

Example 5

(Hydrodecyanation Reaction)

A reaction was carried out in the same way as in Example 4, except that100 g of 2-propanol was used as the solvent and the reaction time wasmade 3 hours. The conversion of 2,3,5,6-tetrafluoroterephthalonitrilewas found to be 89% and the yield of 2,3,5,6-tetrafluorobenzonitrile(based on 2,3,5,6-tetrafluoroterephthalonitrile) was 38%.

Example 6

(Hydrodecyanation Reaction)

By a method similar to Example 1 and using 100 g of toluene, 1.00 g of5% palladium/activated carbon, 0.70 g of ethylenediaminetetraaceticacid, and 5.0 g of 2,3,5,6-tetrafluoroterephthalonitrile, a reaction wascarried out at 100° C. for 22 hours. The conversion of2,3,5,6-tetrafluoroterephthalonitrile was found to be 95% and the yieldof 2,3,5,6-tetrafluorobenzonitrile (based on2,3,5,6-tetrafluoroterephthalonitrile) was 81%.

Example 7

(Hydrodecyanation Reaction)

115 g of toluene, 1.60 g of 5% palladium/activated carbon, 1.20 g offormic acid, and 1.0 g of 2,3,5,6-tetrafluoroterephthalonitrile wereadded to a 500 cc stainless steel autoclave equipped with a Teflon innertube in a nitrogen atmosphere. The gas phase was sufficiently replacedwith hydrogen gas, then the autoclave was sealed and heated to 150° C.After 2 hours, the reaction solution was analyzed by gas chromatography,whereupon the conversion of 2,3,5,6-tetrafluoroterephthalonitrile wasfound to be 99% and the yield of 2,3,5,6-tetrafluorobenzonitrile (basedon 2,3,5,6-tetrafluoroterephthalonitrile) was 63%.

Example 8

(Hydrodecyanation Reaction)

200 g of ethylbenzene, 0.30 g of 5% palladium/activated carbon, and 6.0g of 2,3,5,6-tetrafluoroterephthalonitrile were added to a 1000 ccstainless steel autoclave in a nitrogen atmosphere. The gas phase wassufficiently replaced with a mixed gas of 41 vol % hydrogen and 59 vol %nitrogen, then the mixed gas was used to keep the pressure at 0.23 MPaand the temperature was maintained at 190° C. After 2, 4, and 6 hours,the reaction solution was analyzed by gas chromatography, whereupon theconversions of 2,3,5,6-tetrafluoroterephthalonitrile were found to be23, 62, and 99% and the yields of 2,3,5,6-tetrafluorobenzonitrile (basedon 2,3,5,6-tetrafluoroterephthalonitrile) were 22, 56, and 87%,respectively.

Example 9

(Hydrodecyanation Reaction) 120 of ethyl benzene, 0.67 g of 5%palladium/activated carbon, 13.9 g of2,3,5,6-tetrafluoroterephthalonitrile were added to a 300 cc stainlesssteel autoclave equipped with a reflux condenser in a nitrogenatmosphere. The gas phase was sufficiently replaced with mixed gas of 41vol % hydrogen and 59 vol % nitrogen, then the mixed gas was used tomaintain the pressure at 0.23 MPa and the temperature was maintained at190° C. During the reaction, the pressure was held at 0.23 MPa whilecirculating the above mixed gas at a flow rate of 15 to 30 cc/min. After21 hours, the reaction solution was analyzed by gas chromatography,whereupon the conversion of 2,3,5,6-tetrafluoroterephthalonitrile wasfound to be 91% and the yield of 2,3,5,6-tetrafluorobenzonitrile (basedon 2,3,5,6-tetrafluoroterephthalonitrile) was 73%.

Example 10

(Hydrodecyanation Reaction)

100 g of ethylbenzene and 3.0 g of 5% palladium/activated carbon wereadded to a 1000 cc stainless steel autoclave. The gas phase wassufficiently replaced with hydrogen gas, then hydrogen gas was used toapply a pressure of 0.3 MPa and make the temperature 100° C. andcatalytic pretreatment was carried out for 1 hour. The gas phase wasagain sufficiently replaced with nitrogen, then 3.0 g of the reactionmaterial, that is, 2,3,5,6-tetrafluoroterephthalonitrile was added. Thenitrogen atmosphere was maintained, the autoclave sealed as it was atatmospheric pressure, and the temperature held at 175° C. After 3 hours,the reaction solution was analyzed by gas chromatography, whereupon theconversion of 2,3,5,6-tetrafluoroterephthalonitrile was found to be 100%and the yield of 2,3,5,6-tetrafluorobenzonitrile (based on2,3,5,6-tetrafluoroterephthalonitrile) was 95%. At the same time, 13.4mmol of α-methylbenzylcyanide was produced. This corresponded to 0.95times molar amount relative to the production of2,3,5,6-tetrafluorobenzonitrile.

Example 11

(Hydrodecyanation Reaction)

By a method similar to Example 10 and using 6.0 g of 5%palladium/activated carbon and 3.0 g of3,4,5,6-tetrafluorophthalonitrile, a reaction was carried out at 150° C.After 5 hours, the reaction solution was analyzed by gas chromatography,whereupon the conversion of 3,4,5,6-tetrafluorophthalonitrile was foundto be 12% and the yield of 2,3,4,5-tetrafluorobenzonitrile (based on3,4,5,6-tetrafluorophthalonitrile) was 6%. At the same time, 0.3 mmol ofα-methylbenzylcyanide was produced. This corresponded to 0.3 times molaramount relative to the production of 2,3,4,5-tetrafluorobenzonitriletimes.

Example 12

(Hydrodecyanation Reaction)

By a method similar to Example 11, a reaction was carried out using2,4,5,6-tetrafluoroisophthalonitrile, instead of3,4,5,6-tetrafluorophthalonitrile. After 5 hours, the reaction solutionwas analyzed by gas chromatography, whereupon the conversion of2,4,5,6-tetrafluoroisophthalonitrile was found to be 36% and the yieldof 2,3,4,6-tetrafluorobenzonitrile (based on2,4,5,6-tetrafluoroisophthalonitrile) was 20%. At the same time, 1.1mmol of α-methylbenzylcyanide was produced. This corresponded to 0.35times molar amount relative to the production of2,3,4,6-tetrafluorobenzonitrile.

Example 13

(Hydrodecyanation Reaction)

4.5 g of granulated 5% palladium/activated carbon was packed in astainless steel reaction tube having an inside diameter of 16 mm, thetemperature of the catalyst layer was held at 100° C., and the hydrogengas was circulated for 1 hour at a flow rate of 100 cc/min for catalyticpreprocessing. The hydrogen gas was supplied at a flow rate of 6 cc/minand the nitrogen gas at 100 cc/min and the temperature of the catalystlayer was made 250° C. A toluene solution containing 1.7% by weight of2,3,5,6-tetrafluoroterephthalonitrile was supplied to the reaction tubeby a pump at a flow rate of 70 to 73 g/hr.

The gas distilled off from the reaction tube was condensed and collectedin a cooling tube. The condensate captured from one hour to one and ahalf hours after the start of the supply of the material was analyzed,whereupon the conversion of 2,3,5,6-tetrafluoroterephthalonitrile wasfound to be 100% and the yield of 2,3,5,6-tetrafluorobenzonitrile (basedon 2,3,5,6-tetrafluoroterephthalonitrile) was 77%.

Example 14

(Reaction for Conversion from Cyano Group to Aldehyde Group)

0.5 g of Raney nickel, 0.31 g of a copper acetate 10 hydrate, and 50 mlof water were added to a 500 cc glass three-necked flask with a refluxcondenser in a nitrogen atmosphere. The resulting mixture was stirred at25° C. for 2 hours, then 50 ml of water and methanol were successivelyadded and decanting performed to wash the catalyst. Further, 80 g ofmethanol, 100 g of acetic acid, and 5 g of water as the solvent and 8.75g of 2,3,5,6-tetrafluorobenzonitrile were newly added. The gas phase wassufficiently replaced with hydrogen gas, then a hydrogen balloon wasattached to the top portion of the reflux condenser and the reactioncarried out at 25° C. for 6 hours. The reaction solution was analyzed bygas chromatography, whereupon the conversion of2,3,5,6-tetrafluorobenzonitrile was found to be 100%, the yield of2,3,5,6-tetrafluorobenzaldehyde (based on2,3,5,6-tetrafluorobenzonitrile) was 80%, and the yield of2,3,5,6-tetrafluorobenzyl alcohol was 2%.

Example 15

(Reaction for Conversion from Cyano Group to Aldehyde Group)

150 g of acetic acid, 50 g of 3N aqueous sulfuric acid solution, 0.875 gof 2% palladium/activated carbon, and 8.75 g of2,3,5,6-tetrafluorobenzonitrile were added to a 500 cc glassthree-necked flask with a reflux condenser in a nitrogen atmosphere. Thegas phase was sufficiently replaced with hydrogen gas, then a hydrogenballoon was attached to the top portion of the reflux condenser and thereaction was carried out at 80° C. for 8 hours. The reaction solutionwas analyzed by gas chromatography, whereupon the conversion of2,3,5,6-tetrafluorobenzonitrile was found to be 59%, the yield of2,3,5,6-tetrafluorobenzaldehyde (based on2,3,5,6-tetrafluorobenzonitrile) was 33%, and the yield of2,3,5,6-tetrafluorobenzyl alcohol was 7%.

Example 16

(Reaction for Conversion from Cyano Group to Aldehyde Group)

Using 158 g of methanol, 5.7 g of concentrated sulfuric acid, and 5.0 gof Raney nickel, a reaction was carried out by a method similar toExample 15. When the reaction was carried out at 25° C. for 4 hours, theconversion of 2,3,5,6-tetrafluorobenzonitrile was found to be 80%, theyield of 2,3,5,6-tetrafluorobenzaldehyde (based on2,3,5,6-tetrafluorobenzonitrile) was 44%, and the yield of2,3,5,6-tetrafluorobenzyl alcohol was 1%.

Example 17

(Reaction for Conversion from Cyano Group to Aldehyde Group)

Using 83 g of methanol, 21 g of water, 45 g of formic acid, 1.5 g ofRaney nickel, and 5.0 g of 2,3,5,6-tetrafluorobenzonitrile, a reactionwas carried out by a method similar to Example 15. When the reaction wascarried out at 60° C. for 4 hours, the conversion of2,3,5,6-tetrafluorobenzonitrile was found to be 100% and the yield of2,3,5,6-tetrafluorobenzaldehyde (based on2,3,5,6-tetrafluorobenzonitrile) was 84%.

Example 18

(Reaction for Conversion from Cyano Group to Aldehyde Group)

Using 91 g of methanol, 12 g of water, 45 g of acetic acid, and 0.25 gof Raney nickel, a reaction was carried out by a method similar toExample 17. When the reaction was carried out at 60° C. for 2 hours, theconversion of 2,3,5,6-tetrafluorobenzonitrile was found to be 100% andthe yield of 2,3,5,6-tetrafluorobenzaldehyde (based on2,3,5,6-tetrafluorobenzonitrile) was 70%.

Example 19

(Reaction for Conversion from Cyano Group to Aldehyde Group)

Using 82 g of dioxane, 21 g of water, 45 g of acetic acid, and 0.5 g ofRaney nickel, a reaction was carried out by a method similar to Example18. The conversion of 2,3,5,6-tetrafluorobenzonitrile was found to be100% and the yield of 2,3,5,6-tetrafluorobenzaldehyde (based on2,3,5,6-tetrafluorobenzonitrile) was 47%. The yield of2,3,5,6-tetrafluorobenzyl alcohol was 2%.

Example 20

(Reaction for Conversion from Aldehyde Group to Hydroxymethyl Group)

27 g of dioxane, 9 g of acetic acid, 53 g of water, 1.5 g of Raneynickel, and 3.0 g of 2,3,5,6-tetrafluorobenzaldehyde were added to a 500cc stainless steel autoclave equipped with a Teflon inner tube in anitrogen atmosphere. The gas phase was sufficiently replaced withhydrogen gas, then the pressure was raised to 0.5 MPa (gauge pressure).The reaction was performed at 50° C. for 2 hours, then the reactionsolution was analyzed by gas chromatography, whereupon the conversion of2,3,5,6-tetrafluorobenzaldehyde was found to be 100% and the yield of2,3,5,6-tetrafluorobenzyl alcohol (based on2,3,5,6-tetrafluorobenzaldehyde) was 99%.

Example 21

(Reaction for Conversion from Aldehyde Group to Hydroxymethyl Group)

A reaction was carried out in the same way as in Example 20, except that33 g of methanol, 18 g of acetic acid, 8 g of water, and 2.0 g of2,3,5,6-tetrafluorobenzaldehyde were used and the reaction temperaturewas made 80° C. The conversion of 2,3,5,6-tetrafluorobenzaldehyde wasfound to be 81% and the yield of 2,3,5,6-tetrafluorobenzyl alcohol(based on 2,3,5,6-tetrafluorobenzaldehyde) was 81%.

Example 22

(Reaction for Conversion from Cyano Group to Hydroxymethyl Group)

83 g of methanol, 45 g of acetic acid, 21 g of water, 0.5 g of Raneynickel, and 5.0 g of 2,3,5,6-tetrafluorobenzonitrile were added to a 500cc stainless steel autoclave equipped with a Teflon inner tube in anitrogen atmosphere. The gas phase was sufficiently replaced withhydrogen gas, then the autoclave was sealed and heated to 60° C. Thereaction was carried out for 2 hours, Next, 1.0 g of Raney nickelcatalyst was newly added, the gas sufficiently replaced with hydrogengas, then the pressure raised to 0.5 MPa (gauge pressure). The reactionwas carried out at 80° C. for 2 hours again, then the reaction solutionwas analyzed by gas chromatography, whereupon the conversion of2,3,5,6-tetrafluorobenzonitrile was found to be 100%, the yield of2,3,5,6-tetrafluorobenzyl alcohol (based on2,3,5,6-tetrafluorobenzonitrile) was 57%, and the yield of2,3,5,6-tetrafluorobenzaldehyde was 2%.

Example 23

(Reaction for Conversion from Cyano Group to Hydroxymethyl Group)

2.5 g of Raney nickel and 0.65 g of lead acetate were added and areaction was carried out by a method similar to Example 22 for 2.5hours. Without further adding a catalyst, this is pressurized withhydrogen gas to 0.5 MPa (gauge pressure) as it is and the reaction againperformed at 80° C. for 2 hours, whereupon the conversion of2,3,5,6-tetrafluorobenzonitrile was found to be 100%, the yield of2,3,5,6-tetrafluorobenzyl alcohol (based on2,3,5,6-tetrafluorobenzonitrile) was 48%, and the yield of2,3,5,6-tetrafluorobenzaldehyde was 1%.

Industrial Applicability

According to the present invention, it is possible to produce thefluorinated benzyl alcohol having the general formula (I) and thefluorinated benzonitrile having the general formula (III) by anindustrially advantageous method at a high yield. In particular, it ispossible to produce 2,3,5,6-tetrafluorobenzonitrile and2,3,5,6-tetrafluorobenzyl alcohol useful as production intermediates ofpyrethroids.

We claim:
 1. A process for producing a fluorinated benzonitrile comprising the step of:hydrogenolyzing a fluorinated dicyanobenzene substituted with 1 to 4 fluorine atoms and having the remainder which may be substituted with a chlorine atom in the presence of at least one metal catalyst selected from the group consisting of metals of Group VIII, Group IX, and Group X of the Periodic Table with or without supplying hydrogen gas using an aromatic compound having hydrogen at its α-position as a source of hydrogen at a temperature from room temperature to about 400° C. so as to cause hydrodecyanation of only the cyano group.
 2. A process for producing a fluorinated benzonitrile as claimed in claim 1, wherein the catalyst is at least one metal catalyst selected from the group consisting of metals of Group VIII, Group IX, and Group X of the Periodic Table.
 3. A process for producing a fluorinated benzonitrile as claimed in claim 1, wherein the fluorinated dicyanobenzene is tetrafluoroterephthalonitrile.
 4. A process for producing a fluorinated benzonitrile as claimed in claim 1, wherein a monoalkyl substituted benzene is used as the solvent.
 5. A process for producing a fluorinated benzonitrile as claimed in claim 1, wherein the hydrodecyanation reaction is carried out with or without supplying hydrogen gas using an aromatic compound having hydrogen at its α-position as a source of hydrogen.
 6. A process for producing a fluorinated benzyl alcohol having the formula (I): ##STR13## wherein a and b independently represent 1, 2, 3, or 4 and c represents 0, 1, or 2 comprising the steps of:hydrodecyanating only one of the cyano groups of a fluorinated dicyanobenzene having the formula (II) ##STR14## wherein a, b, and c are defined as above, to produce a fluorinated benzonitrile having the formula (III): ##STR15## wherein a, b, and c are as defined above and then converting the cyano group of the fluorinated benzonitrile to a hydroxymethyl group.
 7. A process for producing a fluorinated benzyl alcohol as claimed in claim 6, wherein the process comprises hydrogenolyzing the fluorinated dicyanobenzene having the above formula (II) in the presence of a catalyst to hydrodecyanate only one cyano group, whereby the fluorinated benzonitrile having the formula (III) is produced, and then reducing the resultant fluorinated benzonitrile or hydrolyzing the resultant fluorinated benzonitrile and reducing the resultant corresponding fluorinated benzoic acid thereby to convert the cyano group to a hydroxymethyl group.
 8. A process for producing a fluorinated benzyl alcohol as claimed in claim 7, wherein the catalyst is at least one metal catalyst selected from the group consisting of metals of Group VIII, Group IX, and Group X of the Periodic Table.
 9. A process for producing a fluorinated benzyl alcohol as claimed in claim 6, wherein the fluorinated dicyanobenzene is tetrafluoroterephthalonitrile.
 10. A process for producing a fluorinated benzyl alcohol as claimed in claim 6, wherein the fluorinated benzonitrile having the formula (III) is reduced to a fluorinated benzaldehyde having the formula: ##STR16## wherein a, b, and c are as defined above, and the aldehyde group of the fluorinated benzaldehyde is then reduced to a hydroxymethyl group.
 11. A process for producing a fluorinated benzyl alcohol as claimed in claim 10, wherein the cyano group of the fluorinated benzonitrile having the above formula (III) is reduced to a hydroxymethyl group by a single stage reaction without isolating the fluorinated benzaldehyde.
 12. A process for producing a fluorinated benzyl alcohol as claimed in claim 6, wherein tetrafluoroterephthalonitrile is used as a starting material and only the cyano group of one side is hydrodecyanated to produce 2,3,5,6-tetrafluorobenzonitrile, followed by converting the cyano group of the 2,3,5,6-tetrafluorobenzonitrile to a hydroxymethyl group so as to produce 2,3,5,6-tetrafluorobenzyl alcohol.
 13. A process for producing a fluorinated benzyl alcohol as claimed in claim 6, wherein a monoalkyl substituted benzene is used as a solvent of the hydrodecyanation reaction.
 14. A process for producing a fluorinated benzyl alcohol as claimed in claim 6, wherein the hydrodecyanation reaction is carried out with or without supplying hydrogen gas using an aromatic compound having hydrogen at its α-position as a source of hydrogen.
 15. A process for producing a fluorinated benzyl alcohol comprising the step of:reducing a fluorinated benzonitrile substituted with 1 to 4 fluorine atoms and having the remainder which may be substituted with a chlorine atom or hydrolyzing the fluorinated benzonitrile and reducing the resultant corresponding fluorinated benzoic acid to convert the cyano group to a hydroxymethyl group.
 16. A process for producing a fluorinated benzyl alcohol as claimed in claim 15, wherein the fluorinated benzonitrile is 2,3,5,6-tetrafluorobenzonitrile. 